Bio-oil is among the most economical approaches for the production of advanced biofuels. However, bio-oil faces several challenges including high acidity, high viscosity and poor storage and thermal stability. This presentation focuses on the development of a stable liquid fuel from the lignocellulosic bio-oil-derived phenolic oil (PO). Our strategy exploits a little-recognized chemistry: the Fischer esterification of PO and carboxylic acids into carboxylic acid phenyl esters (CAPE) using Dean-Stark distillation. The base-catalyzed ester hydrolysis reaction, analysis of the phenolic-OH content by the Folin Ciocalteu method, and the molecular weight determination by gel permeation chromatography suggest the conversion of ~30% PO into its corresponding CAPE. FTIR analysis reveals the formation of esters with more prominent C=O stretching than the original PO, formation of C=O-O and O-C-C stretching, and the disappearance of the phenolic OH bands in the CAPE. These observations were further supported by the NMR analysis which also reveals the formation of the CAPE together with some unreacted precursors. A blend of 20% CAPE with fossil diesel fuel, referred to as py diesel, was successfully burned in a diesel engine. Elevated operating temperature and CO<sub>2</sub> emissions compared to fossil diesel suggest that CAPE has a higher heating value than fossil diesel fuel. Brookfield viscosity analysis indicates CAPE has 330-fold lower viscosity than starting PO. The accelerated laboratory aging test of the CAPE shows little degradation, suggesting reasonable fuel stability. Inclusively, the resulting blended fuel has a resemblance with methyl esters used as biodiesel.

Esterification of phenolic oil for use in diesel engines

ACS Fall 2021

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